JPH086681B2 - Variable displacement radial piston pump - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable displacement radial piston pump adapted as a vehicle height control hydraulic pressure generator for an active suspension of an automobile.

(Prior Art) As a conventional variable displacement radial piston pump, for example, the one described in "Hydraulic Technology Handbook" (1976, published by Nikkan Kogyo Shimbun) on page 257 is known.

In this conventional variable displacement radial piston pump, a rotary cylinder is provided with a plurality of pistons in the radial direction, and the outer end of the piston is inscribed in an eccentric cam ring, so that the piston reciprocates as the rotary cylinder rotates. It is a rotary cylinder type that sucks and discharges fluid by the reciprocating motion of this piston.

When changing the discharge capacity, the casing on the outer periphery is moved to adjust the eccentricity of the eccentric cam ring.

(Problems to be Solved by the Invention) However, in the above-mentioned conventional variable displacement radial piston pump, a structure in which the displacement is varied by moving the casing to change the eccentric amount of the eccentric cam ring,
That is, since the structure is such that the eccentricity adjustment mechanism is added to the large-diameter cam ring, it is required to have a compact capacity, low weight, and low operating force at the same time, although there is a performance requirement of variable capacity as in automobiles. There was a problem that it was inappropriate to adapt to things.

That is, the eccentricity adjusting mechanism becomes large in size and requires an operating force equal to or higher than the fluid pressure (about 100 kgf / cm ² ) acting on the internal piston during the eccentricity operation.

Therefore, the applicant of the present invention intends to solve the above problems.
In the application specification and drawings of No. 63-96614 (filed on July 21, 1988), a variable displacement radial piston pump which obtains a stepwise variable displacement while using a fixed cylinder type radial piston pump was proposed. However, in this prior application, since the discharge amount switching control is performed while connecting the discharge passage and the drain passage at the same time, the following problems remain during the discharge amount switching transition period.

For example, set the large discharge pump to P _L and the small discharge pump to P _S
And in case of a P _L by the switching valve from the small discharge state to connect the discharge passage P _S connected to the drain passage, the large discharge state connected to the drain passage P _S connecting the P _L to the discharge flow path during Setsu換Ru, P _L has to replace connecting the discharge passage closed drain passage.

At this time, close the drain passage above, since the switching valve is provided in a position downstream of the check valve, the discharge fluid of the pump P _L is confined, the fluid pressure is abnormally increased, leading to deterioration of the pump life However, if the connection between the drain passage and the discharge passage is overlapped, the pressurized fluid in the discharge passage will flow into the drain passage, causing an abnormal decrease in fluid pressure. It will cause abnormal operation.

The present invention has been made in view of the above problems, and simultaneously satisfies the performances of compactness, low weight, and low operating force required for adapting to an automobile, etc. The development of a variable displacement radial piston pump that can obtain multi-stage variable displacement without abnormal increase or decrease in fluid pressure in the above.

(Means for Solving the Problems) In order to solve the above problems, a variable displacement radial piston pump according to the present invention has a piston pump composed of one set of pistons and a fixed cylinder of the radial piston pump as a minimum unit, and has the same discharge amount or A plurality of different N (N is a natural number of 2 or more) sets are divided, a plurality of fluid discharge channels are formed for each of the divided sets, and a reverse flow to the piston pump side is formed in each of the plurality of fluid discharge channels. A check valve for preventing the above, each of the plurality of discharge fluid paths upstream of the check valve, branching a plurality of drain flow paths toward the reserve tank, in the middle of the plurality of drain flow paths, The maximum number of stages is the number that can be set as different discharge amounts for a plurality of N sets alone or in combination (M is a natural number of 2 or more) that is greater than or equal to 2 and less than or equal to the maximum In order to obtain the discharge amount in stages, a switching valve having an open / closed selection position of the drain flow path that matches the number of M is provided.

(Operation) In order to obtain a different discharge amount when the radial piston pump is operating, switching control is performed on the switching valve provided in the drain passage.

For example, when a piston pump having one set of pistons and a fixed cylinder is set as a minimum unit, and a group that constitutes a large-capacity pump P _L and a group that constitutes a small-capacity pump P _S with different discharge amounts are divided, the switching valve has a large-capacity discharge When switching to the position where only the flow passage or the small-capacity discharge flow passage is selected, a large-capacity or small-capacity discharge amount is obtained, and when the switching valve is switched to the position where the large-capacity discharge flow passage and the small-capacity discharge flow passage are added. The total discharge amount can be obtained.

Therefore, it is possible to obtain a gradually variable discharge volume while simultaneously satisfying the performances of compactness, low weight, and low operating force.

 Next, the operation during the capacity switching transition period will be described.

For example, set the large discharge pump to P _L and the small discharge pump to P _S
In case of a, during Setsu換Ru from the small discharge state to connect the discharge passage P _S connecting the P _L to the drain passage, the large discharge state for connecting connects the P _L to the discharge flow path P _S to drain passage , P _L has to replace connecting the discharge passage closed drain passage.

At this time, even close the drain passage above, since the drain flow path switching valve is provided which is provided in a position upstream of the check valve, without discharging fluid of the pump P _L is confined, the predetermined pressure or more Then, the discharge fluid is supplied after passing through the check valve, and the abnormal increase in fluid pressure is prevented.

Also, when the drain passage is closed and the connection with the discharge passage overlaps, the drain passage branched from the discharge passage has a branch point on the pump side upstream of the check valve. The fluid pressure temporarily decreases in the flow passage on the upstream side of the check valve, and the check valve closes due to the pressure difference between the upstream side and the downstream side of the check valve as the fluid pressure decreases. The abnormal reduction of the fluid pressure supplied to the fluid pressure actuator is prevented.

(Example) Hereinafter, the Example of this invention is described based on drawing.

 First, the configuration will be described.

FIG. 1 shows a variable displacement radial piston pump A according to an embodiment.
Fig. 2 is a schematic diagram showing the discharge amount with the minimum unit being the piston pump consisting of one set of fixed cylinder type radial piston pump P _{RP in which} the piston in the fixed cylinder reciprocates radially with an eccentric cam that rotates Are divided into different large capacity pumps P _L and small capacity pumps P _S ,
A large-capacity fluid discharge passage 1 and a small-capacity fluid discharge passage 2 are formed for each of the divided pumps P _L and P _S.

Check valves 3 and 4 for preventing backflow to the large-capacity pump P _L and the small-capacity pump P _S , respectively, in both the fluid discharge flow paths 1 and 2.
Is provided.

It should be noted that both fluid discharge passages 1 and 2 merge on the downstream side of the check valves 3 and 4 to form a variable capacity discharge passage 6 having an accumulator 5 in the middle.

Further, two drain passages 8 and 9 toward the reserve tank 7 are branched at the upstream sides of the check valves 3 and 4 of the fluid discharge passages 1 and 2, respectively.

Then, in the middle of the drain flow paths 8 and 9, a three-position switching valve 11 for obtaining a discharge amount in three stages by opening / closing the drain flow paths 8 and 9 and the drain flow path 10 directly connected to the reserve tank 7. Is provided.

Next, the variable displacement radial piston pump A will be described with reference to a specific example shown in FIG.

The variable displacement radial piston pump A is a unit in which the constituent elements surrounded by the dotted line in FIG. 1 are assembled, and when FIG. 1 and FIG. 2 are associated, 12 is an intake port and 13 is a discharge port. , 14 are drain ports.

That is, the large-capacity pump P _L and the small-capacity pump P _S are provided in the same casing 15 so as to operate by receiving the driving force from the same drive shaft 16, and the large-capacity pump P _L is composed of 6 sets. Small capacity pump consisting of piston and fixed cylinder
P _S is composed of six sets of pistons and fixed cylinders that are arranged in alternating positions so as to overlap with the pistons and fixed cylinders of the large capacity pump P _L.

In addition, as a method of making the capacities of both pumps P _L and P _S different, as described in the previous Japanese Patent Application No. 63-96614, the discharge capacities of the respective pumps and fixed cylinders of both pumps P _L and P _S If the pumps and the fixed cylinder have the same discharge capacity for both pumps P _L and P _S , use different techniques such as different eccentricity or different piston suction side port positions. To do.

The three-position switching valve 11 has a stepping motor 17 as an actuator, and is fixedly provided in the casing 12.

Next, the structure of a specific example of the 3-position switching valve 11 shown in FIG. 3 will be described.

The 3-position switching valve 11 has a valve case 21 in which a stepping motor 17 is fixed and a valve hole 20 is formed.
A fixed cylinder 22 fixed to the valve hole 20 and having a large-capacity port 22a, a small-capacity port 22b and a drain port 22c, and a rotary screw shaft 23 of the stepping motor 17, which is screwed into a fixed position. It is slidable in the axial direction of the motor and is constituted by a spool 24 having a spool hole 24a formed at one position. Reference numeral 25 in the drawing denotes a rotation stop pin of the spool 24.

 Next, the operation of the embodiment will be described.

(A) In the small capacity mode (in the I mode) When the 3-position switching valve 21 is set to the I position by an operation command from the outside to the stepping motor 17, as shown in the upper position of the spool 24 in FIG. Port 22a and spool hole 24a communicate with each other, and discharge passage 1 of large-capacity pump P _L
Communicates with been drain passage 8 and drain passage 10 branches from the discharge flow rate from a high volume pump P _L will be all returned to the reserve tank 7.

Further, since the small-capacity port 22b is being closed by the spool 24, the discharge flow rate from the small capacity pump P _S is supplied to the variable capacitance discharge passage 6 has passed the discharge passage 2 → the check valve 4 It will be.

Therefore, when the 3-position switching valve 21 is set to the I position, only the small capacity pump P _S discharges, and the small capacity characteristic I of FIG. 4 is obtained.

In the discharge flow rate characteristic, the discharge flow rate is flat on the high rotation side because the self-priming property of the radial piston pump is deteriorated and the discharge flow rate reaches a peak.

(B) In the large capacity mode (II mode) When the 3-position switching valve 21 is set to the II position by an operation command to the stepping motor 17 from the outside, the small capacity port 22b and the spool hole 24a communicate with each other in FIG. The drain passage 9 branched from the discharge passage 2 of the small capacity pump P _S
And the drain flow path 10 communicate with each other, and all the discharge flow rate from the small capacity pump P _S is returned to the reserve tank 7.

Further, since the large-capacity port 22a being closed by the spool 24, the discharge flow rate from a high volume pump P _L is supplied to the variable capacitance discharge passage 6 has passed the discharge channel 1 → the check valve 3 It will be.

Therefore, when the 3-position switching valve 21 is set to the II position, the discharge is performed only by the large capacity pump P _L , and the large capacity characteristic II of FIG. 4 is obtained.

(C) In the total capacity mode (in the III mode) When the 3-position switching valve 21 is set to the III position by an operation command to the stepping motor 17 from the outside, as shown in the lower position of the spool 24 in FIG. Both the port 22a and the small capacity port 22b are closed by the spool 24.

Therefore, when the 3-position switching valve 21 is set to the III position,
The discharge flow rate from the large capacity pump P _L and the small capacity pump P _S is
Both discharge flow paths 1 and 2 → Both check valves 3 and 4 are passed to be supplied to the variable capacity discharge flow path 6, and the discharge capacity is the sum of the discharge capacities of both pumps. A total capacity characteristic III of is obtained.

(D) Mode switching For example, when the 3-position switching valve 21 is switched from the I position to the II position, the spool 24 closes the large capacity port 22a first so that the small capacity port 22b and the spool hole 24a communicate with each other. The case of delay will be described.

In this case, the drain flow path 8 branched from the discharge flow path 1
Since a branch point is set on the pump side upstream of the check valve 3, when the fluid pressure between the discharge flow passage 1 and the drain flow passage 8 exceeds a predetermined pressure due to the closing of the large capacity port 22a, the reverse Stop valve 3
After that, the fluid is supplied to the variable discharge passage 6.

Therefore, a large capacity pump in a closed on the downstream side of the check valve 3 P _L
The abnormal increase in fluid pressure due to the confined discharge fluid is not generated.

Further, in the case of switching the 3-position switching valve 21 from the I position to the II position, when the large capacity port 22a is closed by the spool 24, the communication between the small capacity port 22b and the spool hole 24a overlaps, Described below is the case where the discharge fluid from both pumps P _L and P _S is drained.

In this case, the drain flow path branched from the discharge flow paths 1 and 2
Since 8 and 9 have a branch point on the pump side upstream of the check valves 3 and 4, the fluid pressure in the flow passage on the upstream side of the check valves 3 and 4 temporarily decreases. As the pressure decreases, the check valves 3 and 4 are closed due to the pressure difference between the upstream side and the downstream side of the check valves 3 and 4.

Therefore, the fluid pressure in the variable discharge passage 6 is abnormally reduced,
The operating accuracy of the actuator that operates using this fluid pressure is not deteriorated.

As described above, in the variable displacement radial piston pump A of the embodiment, since the fixed cylinder type radial piston pump P _RP is used to obtain the stepwise variable displacement, the outer casing is moved. Compared to a pump that obtains a variable capacity by adjusting the eccentricity of the eccentric cam ring,
The compact, low weight, and low operating force are achieved at the same time, and high adaptability to automobiles can be obtained.

In addition, the drain passages 8 and 9 branched from the discharge passages 1 and 2 have branch points set on the pump side upstream of the check valves 3 and 4, and the drain passages 8 and 9 have three positions in the middle. Since the switching valve 11 is provided to control the switching of the discharge amount, there is no abnormal increase or decrease in the fluid pressure during the transition period of the discharge amount switching. It is possible to prevent a decrease in control accuracy of the vehicle height control of the suspension.

The embodiment of the present invention has been described in detail above with reference to the drawings.
The specific configuration is not limited to this embodiment, and the present invention includes a design change and the like within a range not departing from the gist of the present invention.

For example, although the embodiment shows an example in which the pump is divided into two sets of a large capacity pump and a small capacity pump, it is divided into three groups of a large capacity pump, a medium capacity pump and a small capacity pump, and four or more kinds of discharge amounts are provided. Alternatively, see the specification and drawings of Japanese Utility Model Application No. 63-96614 for the specific method of varying the capacity.

Further, in the embodiment, the example of the three-position switching valve 21 shown in FIG. 3 is shown as the switching valve, but a fifth modification which is a modification thereof.
It may be the three-position switching valve 30 shown in the figure, or
As shown in FIG. 6, a combination of a first solenoid valve 31 and a second solenoid valve 32 having a two-position switching valve structure may be used.

As shown in FIG. 5, the three-position switching valve 30 has a stepping motor 17 fixed thereto, a valve case 41 having a valve hole 40 formed therein, and a large capacity port 42a fixed to the valve case 40. And a fixed cylinder 42 in which a small capacity port 42b and a drain port 42c are formed and a rotary screw shaft 43 of the stepping motor 17 are screwed together and slidable in the motor axial direction in a screwed positional relationship. The spool 44 includes 44a and 44b, a guide pin 45 for slidingly guiding the spool 44, and a rotation stop pin 46 for the spool 24.

(Effects of the Invention) As described above, in the variable displacement radial piston pump of the present invention, the piston pump by one set of pistons of the radial piston pump and the fixed cylinder is the minimum unit, and the discharge amount is the same or different. Multiple N
(N is a natural number of 2 or more), and a plurality of fluid discharge passages are formed for each of the divided sets to prevent backflow to the piston pump side in each of the plurality of fluid discharge passages. A check valve is provided, and a plurality of drain flow paths to the reserve tank are branched to upstream of the check valves of the plurality of fluid discharge flow paths, and the drain flow path is opened and closed in the middle of the plurality of drain flow paths. Since a switching valve is provided to obtain a discharge amount of M (M is a natural number of 2 or more) stages by selection, the compactness, low weight, and low operating force required for adapting to automobiles and the like are simultaneously satisfied, and yet The effect that a multi-stage variable capacity can be obtained without abnormal increase or decrease in fluid pressure during the transition period of the discharge amount switching is obtained.

[Brief description of drawings]

FIG. 1 is a schematic view of a variable displacement radial piston pump of an embodiment of the present invention, FIG. 2 is an external view of a variable displacement radial piston pump of the embodiment, and FIG. 3 is a three-position switching valve adapted to the embodiment pump. FIG. 4 is a sectional view showing the discharge flow rate characteristic of the embodiment pump, FIG. 5 is a sectional view showing a modification of the 3-position switching valve, and FIG. 6 is a solenoid valve having a 2-position switching structure as a switching valve. It is a figure which shows the example comprised by combining three. A: Variable displacement radial piston pump P _RP (fixed cylinder type) Radial piston pump P _L: Large displacement pump P _S: Small displacement pump 1,2 ... Discharge passage 3,4 ... Check valve 5 …… Accumulator 6 …… Variable capacity discharge passage 7 …… Reservoir tank 8,9,10 …… Drain passage 11 …… 3 Position switching valve (switching valve)

Claims (1)

[Claims] 1. A radial piston pump having a set of pistons and a fixed cylinder as a minimum unit, and divided into a plurality of N (N is a natural number of 2 or more) sets having the same or different discharge amounts. A plurality of fluid discharge passages are formed for each set, and a check valve for preventing backflow to the piston pump side is provided in each of the plurality of fluid discharge passages. A plurality of drain flow paths that branch toward the reserve tank are branched to each of the sides, and the maximum number that can be set as a different discharge amount by the single or combination of the plurality N sets is provided in the middle of the plurality of drain flow paths. In order to obtain a discharge amount of M stages (M is a natural number of 2 or more) that is 2 or more and equal to or less than the maximum number of stages, a switching valve having a drain channel opening / closing selection position that matches the number of Ms. Variable displacement radial piston pump, characterized in that the provided.